Sepsis is acute organ dysfunction in the setting of infection. An accurate diagnosis is important to guide treatment and disposition. Tissue oxygen saturation (StO2) can be estimated noninvasively by near-infrared spectroscopy (NIRS), and may be an indicator of microcirculatory dysfunction in early sepsis. We aimed to determine the utility of StO2 for sepsis recognition and outcome prediction among patients presenting to the emergency department (ED) with infection.